In the Giant Bomb interview, Phil said that the leaked info a couple of weeks ago impacted their decision to come out with this. They didn't want to have to continue to straight-face deny what was going on, when everyone basically knew the truth.
This lets them do their work getting the console made and working right without the cloak and dagger stuff.
I imagine if there was only baseless rumors going around, they would have kept quiet, or at most been very vague "Great things to come!".
I haven't seen the interview with Phil yet but this makes sense. The second "Project Scorpio" flashed on the E3 screen it hit me MS basically didn't have a choice after the leaks.
Pulling back a bit, there's a lot of very smart people in here over-thinking this situation. When you combine that with the requisite console warrior silliness that always breaks out like some nerd version of Hatfields vs McCoys we're bound to end up with unnecessary negativity that makes it difficult to be objective (usually because it devolves into list wars).
Bottom line: People are going to read into the Scorpio reveal in a few different ways based on personal biases, but ultimately MS is so far behind sales-wise it's reasonable to assume announcing Scorpio early isn't going to make things too much worse, if at all. I don't see this as a "White Flag" so much as "Well played Sony, you took round 1. Now we let's reset the game board for Round 2." MS does have the financial might to essentially cut the Xbone loose early and move on. Judging by reactions of friends who are more average "Dude Bro" than NeoGAF nerd like most of us, the XBone S and Scorpio messaging seems to have been pretty effective and even exciting in getting across the "Beyond Generations" idea that both Sony and MS seem to be moving towards. Accessories and games that continue to be backward/forward compatible as new hardware iterations come out, offering different configs at different price-points, etc...is a pretty easy idea to understand. I don't think this has to be read into as Doom and Gloom.
That said, Sony really brought it with several *games* that generally appeal to me more than most of what I saw from MS. Horizon, for example, is my game of E3, far and away (tho Zelda Wii U looks pretty amazing as well). Honorable mention to Days Gone. God of War, Death Stranding, and Spider-Man all look great too.
In contrast, while I was excited by MS's hardware reveals, I was admittedly somewhat disappointed with most of what MS had to show in terms of games. I thought MS's presentation was really well done...an awesome production... but the Scalebound and Gears 4 gameplay trailers were straight up boring. Sea of Thieves also looked kinda "meh". Maybe my opinion will change on one or all of these over time. Dead Rising 4 looks cool...but it's yet another Dead Rising and I've yet to even finish DR3. To my tastes, We Happy People was easily the best of the Xbox games I had a chance to see (major Bioshock 1 vibes) And I'm probably most excited about State of Decay 2 (altho they didn't have a lot to show I'm just stoked about 4-player co-op = gimme, gimme, gimme).
Basically, I think we should give MS a break on their Scorpio announcement. It makes sense within context. IMHO any real criticism should be leveled at how their exclusives games lineup looked kinda thin compared to Sony (which, of course, is totally subjective). I much prefer the XBL online/social experience and the Xbone controller. But I just call 'em like I see 'em...and to my eyes Sony's exclusive list looks straight up fuckin awesome right now.
